In recent year, comparatively thin display devices such as liquid crystal display devices have been widely used in various types of information terminal such as electronic book terminals, smartphones, cellular phones, PDAs (portable information terminals), laptop personal computers, portable game machines, and car navigation apparatuses. These display devices are accompanied by issues such as reduction in electric power consumption and improvement in display image quality. Under such circumstances, there have been proposed various technologies intended to solve these issues accompanying display devices.
An example of a technology for improving display image quality is a method of raising a refresh rate. For example, increasing the refresh rate from “60 Hz (i.e. 60 fps)” to “120 Hz (i.e. 120 fps)” in displaying a moving image makes it possible to express a smoother movement and restrain a display defect such as flicker from occurring.
However, as the refresh rate rises, the number of times the display panel is scanned increases accordingly. This results in increased electric power consumption. For this reason, in a case where more emphasize is put on reduction in electric power consumption than on improvement in display image quality, a technology of lowering the refresh rate may be used.
For example, Patent Literature 1, listed below, discloses a technology for reducing electric power consumption by actively speeding up the refresh rate during a time when a pseudo-contour is likely to appear or during a display of a picture in which such a pseudo-contour is conspicuous and by actively lowering the refresh rate in a case where a pseudo-contour is unlikely to appear or in the case of a picture in which a pseudo-contour, if any, is inconspicuous.
Meanwhile, it has been known about liquid crystal display devices that when the write time is of short duration with respect to the response time of liquid crystals, there is a decrease in the rate of voltage retention of the liquid crystals, and the decrease eventually leads to a reduction in contrast ratio. Especially in recent years, since there has been a remarkable increase in resolution of display panels and, accordingly, there has been shortening of the time required to write to each scanning line, such a problem has been likely to take place.
In order to solve such a problem, Patent Literature 2, listed below, discloses a technology for raising the rate of voltage retention of liquid crystals by performing writing twice on each scanning line with a two-wire simultaneous drive method (double scanning).